The present invention relates generally to electro mechanical machinery, and more particularly, to an improvement to such machinery utilizing a disc-type electrical assembly, usually serving as an armature.
Electric DC motors have experienced difficulty in finding acceptance in certain types of applications requiring a high operating torque, such as vehicles, lawn mowers and certain types of tools. Until the present invention, it was not possible to achieve sufficient torque and reasonable efficiency with a machine of sufficiently compact size. Efficiency is particularly important because of the relatively limited nature of the DC power source, typically a battery.
U.S. Pat. No. Re. 33,628 issued on Jul. 2, 1991, discloses a particularly efficient electro mechanical machine which has a field producing assembly, which serves as a stator and is mounted in a housing so as to define an axial air gap which is circumferentially disposed about an axis of rotation. The field assembly is structured to produce a circumferential distribution of magnetic flux in the air gap having P periodic extremes of flux density about the axis. A disc-shaped electrical assembly, serving as an armature is positioned in the air gap, and mounted so that the armature and field assembly are rotatable relative to each other. The armature has a circular array of C non-overlapping coils on each of its front and back faces, the coils on one face being angularly offset from the coils on the other face and each having the same arcuate extent, smaller than 360 degrees divided by P. The coils are arranged in groups of serially connected coils with each group occupying an unique area of an armature face. Inasmuch as adjacent coils are exposed to opposite extremes of the flux, they must have current flow in opposite directions. This is achieved by winding adjacent coils in opposite directions.
The present invention realizes improvements to the machine disclosed in U.S. Pat. No. RE 33,628 which substantially increases the torque and horsepower obtained with a machine of a given diameter and form factor. In accordance with the present invention, an electromechanical machine has a field producing assembly in a cup-shaped air gap which is circumferentially disposed about an axis of rotation. The field assembly produces a circumferential distribution of magnetic flux in the cup-shaped air gap having n periodic extremes of flux density about the axis. A cup-shaped electrical assembly or armature is disposed in the air gap and the armature and field assembly are relatively rotatable. The armature has a circular array of C non-overlapping coils on each of its inner and outer faces with the coils on one face being angularly offset from the coils on the other face. Moreover, since the air gap and coils are cup-shaped, it is possible to achieve, for a machine of given diameter and form factor, a horsepower and torque which was heretofore possible only with substantially larger disk-type motors. That is because the total volume of the air gap and coils correspond to those of a much larger diameter disk-type motor. The savings in cost, weight and size are significant, not to mention the more efficient use of energy.